I. Field of the Invention
Embodiments of the present invention relate generally to delivery devices and procedures for treating a localized abnormal dilation of a lumen, aneurysm, fistula, lesion or the like in certain blood vessels and internal organs. In particular, embodiments are directed to devices and methods for delivering and deploying stent-grafts in the vasculature of a patient, such as for usage in over-the-wire delivery.
II. Description of the Related Art
Various conventional braided wire stents and grafts exist to address various medical conditions in a patient's vasculature. Transluminal prostheses are well known in the medical arts for implantation in blood vessels, biliary ducts, or other similar organs of the living body. These prostheses are commonly known as stents and are used to maintain, open, or dilate tubular strictures or to support tubular structures. When bio-compatible materials are used as a covering or lining for the stent, the prosthesis is called a stent-graft or vascular graft.
Various conventional delivery systems exist for implanting or deploying braided or self-expanding stents or grafts. For example, a braided, self-expanding stent or a graft incorporating a self-expanding stent as a structural component (referred to herein as a stent-graft) may be introduced into the body by stretching the device axially, until its radial diameter is reduced sufficiently so that it can be fed into a catheter. The device is delivered through the catheter to the site of deployment and then released from the catheter whereupon the device self-expands. A simple delivery device for locating and deploying such a device may include a flexible catheter having a proximal handle and a flexible plunger having a proximal handle. The device is inserted into the distal end of the catheter and the distal end of the catheter is positioned at the site of deployment, such as an artery. The handles of the catheter may be moved relative to each other to push out or uncover the device from the distal end of the catheter.
As mentioned above, as a self-expanding stent-graft is deployed from a delivery device, the diameter of the stent-graft expands and draws the ends of the device closer to each other. In other words, the length l2 of the stent-graft when it is in an expanded state (e.g., deployed from the delivery device) is shorter than the length l1 of the stent-graft when it is in a contracted state (e.g., undeployed from the delivery device). An illustration of the relative lengths l1, l2 of a self-expanding stent-graft is shown in FIG. 1.
As a result of the shortened length l2 of the expanded stent-graft (i.e., foreshortening), the placement of the stent-graft within a body lumen can be negatively affected. This is because although the distal end 15 of the stent-graft 5 (i.e., the end farthest inside the body) may be positioned in the desired location P before it is deployed from the delivery system (i.e., in the contracted state), as the stent-graft is deployed and self-expands, for example through movement of a sheath 10 in a direction A as depicted in FIG. 2 to uncover the stent-graft, the distal end 15 of the stent-graft typically moves back towards the delivery device in a direction B. To compensate for this movement and to reposition the end 15 of the stent-graft 5 in the desired location P, the user may have to move a pusher 18 of the delivery device in a direction C, as shown. As a result, a tip of the pusher 18 guiding the deployment of the stent-graft 5 may end up extending farther distally than originally anticipated and in some cases may disturb or damage the patient's vasculature.
Accordingly, there is a need for an improved delivery system that provides predictable placement of a graft in the vasculature and overcomes the shortcomings of conventional solutions.